1. Field of the Invention
The present invention relates to a method for producing biphenyl and its derivative by oxidative coupling of a benzene aromatic compound in a reaction system containing a palladium salt, a copper salt, and a bidentate ligand compound capable of forming a complex with the palladium salt via the nitrogen atom and the oxygen atom present in its molecule and in an atmosphere containing molecular oxygen preferably at a high temperature. More particularly, it relates to a method for selectively producing an asymmetrically substituted biphenyl derivative such as a 2,3,3′,4′-biphenyltetracarboxylic acid tetraester (hereinafter abbreviated as a-BPTT) by using a substituted aromatic compound such as a phthalic diester as the benzene aromatic compound.
2. Description of Related Art
JP-A-55-141417 proposes a process of preparing a biphenyl which comprises oxidatively coupling a benzene aromatic compound in a molecular oxygen atmosphere in the presence of an organopalladium salt and an organocopper salt. Applying the process to oxidative coupling of a phthalic diester yields a 3,3′,4,4′-biphenyltetracarboxylic acid tetraester (hereinafter abbreviated as s-BPTT) and an a-BPTT with the production ratio of the former being higher than that of the latter.
JP-A-61-106541 proposes a method for improving production selectivity to an asymmetrically substituted biphenyl derivative such as an a-BPTT in oxidative coupling of a substituted aromatic compound such as a phthalic diester. However, this method requires continuous or intermittent replenishment of the reaction system with a β-diketone as a ligand with the progress of the reaction.